I found CO in tanks

[2airishuman]

I believe you made the right call as well. It is interesting that the industry hasn't clearly defined what an acceptable level of CO is in a tank, so defaulting to "0" is reasonable. I have detected trace amounts... like .01... and dove.

The Grade E standard is 10 PPM max. I don't believe there is any medical evidence that 10 PPM is hazardous, although there's plenty of speculation that it could be.

http://airtesting.com/wp-content/uploads/2017/04/Breathing-Air-Specifications-2017-2.pdf

Ambient air will often contain that amount, especially in urban environments.

While that is true, the filtration system downstream of a dive compressor should remove it to < 1 PPM if it is working properly.

 

[grf88]

I wonder how many people are diving that level of contamination every day without knowing it.

 

[2airishuman]

I'm not a stickler for 0ppm depending on the compressor. I.e. a stock rix will never put out 0ppm air because it's in ambient air and it doesn't really have "filters" just coalescers that won't remove any CO.

Depends on the setup, I guess, I would expect a rix to have some hopcalite even if a smaller amount than an oil lubricated compressor.

 

[49north]

I believe you made the right call as well. It is interesting that the industry hasn't clearly defined what an acceptable level of CO is in a tank, so defaulting to "0" is reasonable. I have detected trace amounts... like .01... and dove. Ambient air will often contain that amount, especially in urban environments.

Regarding "naming" the operation, you are correct not to do so. You don't specify if these are your own tanks or rentals. If rentals, they may have been filed elsewhere while being used. If they are your own tanks, then you will obviously want to be certain that your tanks weren't already dirty.

Presumably the shop is checking out their system now... Hopefully.

These were rental tanks as we are on vacation.

 

[2airishuman]

We just aborted a dive this morning. We analyzed our tanks with a Palm CO analyzer and found all of the air tanks contained between 6 and 7 ppm. The ambient air read 0 and the nitrox tanks read 0. The dive op said it was our analyzer because the compressor was serviced 22 hours ago. Hmmm...

They offered to give us nitrox, but one member of our group was not nitrox certified, so we declined.

I feel we made the right call. Breathing gas should not have any CO. There doesn’t seem to be any firm numbers as to what is acceptable, but it seems the consensus on this board is 5ppm max.

Does anyone have any thoughts on our decision?

I have a couple of thoughts.

1. I personally would consider a cylinder known to be 6-7 ppm CO to be marginally safe. Whether I would dive it would depend on the circumstances of the dive. I have good cardiovascular health and would probably dive such a cylinder on a one-time basis rather than cancel the dive, if no better alternative was practicable, and the dive was not unusually deep or long. I would consider the availability of nitrox with a CO level below the detection threshold of a portable analyzer to be a practicable alternative.
   
   
2. I believe it would be appropriate to name and shame any dive op that did not take a report of 6-7 ppm CO seriously by taking some sort of action to confirm and correct the problem. CO contamination can vary from one cylinder to the next but at a minimum the dive op could be expected to test other cylinders and the bank system with a handheld tester and check for obvious problems like the wrong filter installed during service.

 

[tbone1004]

Depends on the setup, I guess, I would expect a rix to have some hopcalite even if a smaller amount than an oil lubricated compressor.

stock rix SA-6 as sold by rix and used by the military and many others do not have any filter cartridges.
They have a pair of coalescers, one after the 2nd stage and one after the 3rd stage to remove water, but that is it. Most all contaminants will fall out with the water.

If you see any filter cartridges on a Rix, they were put on after the fact.

 

[2airishuman]

Without any cartridges at all, the air would fail Grade E on dewpoint, would it not? A coalescer alone won't wring out all the water. That's why there is molecular sieve.

 

[tbone1004]

Without any cartridges at all, the air would fail Grade E on dewpoint, would it not? A coalescer alone won't wring out all the water. That's why there is molecular sieve.

I don't think the military was particularly concerned about making grade e air for spec ops on an inflatable boat....
That said, I can 100% confirm that Rix does not have any sort of filtration on their SA series other than the coalescers, and a 10 micron inlet filter

 

[kelemvor]

Presumably the shop is checking out their system now... Hopefully.

That seems unlikely since they told him the problem was his analyzer. Which is the reason I suggested he should name the OP.

 

[Stoo]

That seems unlikely since they told him the problem was his analyzer. Which is the reason I suggested he should name the OP.

LOL... After hours, I meant.... ;-)